<h1>My App</h1>
<p>This is a test page</p>
<div>Width:</div>
<div id="j_width"></div>
<div>Height:</div>
<div id="j_height"></div>
<script>
  document.getElementById('j_width').innerText = window.innerWidth;
  document.getElementById('j_height').innerText = window.innerHeight;
</script>
</body>